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481 lines
14 KiB
C++
481 lines
14 KiB
C++
//
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// 6560.hpp
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// Clock Signal
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//
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// Created by Thomas Harte on 05/06/2016.
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// Copyright © 2016 Thomas Harte. All rights reserved.
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//
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#ifndef _560_hpp
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#define _560_hpp
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#include "../../Outputs/CRT/CRT.hpp"
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#include "../../Outputs/Speaker.hpp"
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namespace MOS {
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/*!
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The 6560 Video Interface Chip ('VIC') is a video and audio output chip; it therefore vends both a @c CRT and a @c Speaker.
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To run the VIC for a cycle, the caller should call @c get_address, make the requested bus access
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and call @c set_graphics_value with the result.
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@c set_register and @c get_register provide register access.
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*/
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class MOS6560 {
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public:
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MOS6560() :
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_crt(new Outputs::CRT::CRT(65*4, 4, Outputs::CRT::NTSC60, 1)),
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_speaker(new Speaker),
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_horizontal_counter(0),
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_vertical_counter(0),
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_cycles_since_speaker_update(0),
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_is_odd_frame(false)
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{
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_crt->set_composite_sampling_function(
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"float composite_sample(usampler2D texID, vec2 coordinate, vec2 iCoordinate, float phase, float amplitude)"
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"{"
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"uint c = texture(texID, coordinate).r;"
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"float y = float(c >> 4) / 4.0;"
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"uint yC = c & 15u;"
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"float phaseOffset = 6.283185308 * float(yC) / 16.0;"
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"float chroma = cos(phase + phaseOffset);"
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"return mix(y, step(yC, 14) * chroma, amplitude);"
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"}");
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// default to NTSC
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set_output_mode(OutputMode::NTSC);
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// show only the centre
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_crt->set_visible_area(_crt->get_rect_for_area(16, 237, 11*4, 55*4, 4.0f / 3.0f));
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_speaker->set_input_rate(255681.75); // assuming NTSC; clock rate / 4
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}
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std::shared_ptr<Outputs::CRT::CRT> get_crt() { return _crt; }
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std::shared_ptr<Outputs::Speaker> get_speaker() { return _speaker; }
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enum OutputMode {
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PAL, NTSC
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};
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/*!
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Sets the output mode to either PAL or NTSC.
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*/
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void set_output_mode(OutputMode output_mode)
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{
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uint8_t luminances[16] = { // range is 0–4
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0, 4, 1, 3, 2, 2, 1, 3,
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2, 1, 2, 1, 2, 3, 2, 3
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};
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uint8_t pal_chrominances[16] = { // range is 0–15; 15 is a special case meaning "no chrominance"
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15, 15, 5, 13, 2, 10, 0, 8,
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6, 7, 5, 13, 2, 10, 0, 8,
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};
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uint8_t ntsc_chrominances[16] = {
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15, 15, 2, 10, 4, 12, 6, 14,
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0, 8, 2, 10, 4, 12, 6, 14,
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};
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uint8_t *chrominances;
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Outputs::CRT::DisplayType display_type;
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switch(output_mode)
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{
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case OutputMode::PAL:
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chrominances = pal_chrominances;
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display_type = Outputs::CRT::PAL50;
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_timing.cycles_per_line = 71;
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_timing.line_counter_increment_offset = 0;
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_timing.lines_per_progressive_field = 312;
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_timing.supports_interlacing = false;
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break;
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case OutputMode::NTSC:
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chrominances = ntsc_chrominances;
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display_type = Outputs::CRT::NTSC60;
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_timing.cycles_per_line = 65;
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_timing.line_counter_increment_offset = 65 - 33; // TODO: this is a bit of a hack; separate vertical and horizontal counting
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_timing.lines_per_progressive_field = 261;
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_timing.supports_interlacing = true;
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break;
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}
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_crt->set_new_display_type((unsigned int)(_timing.cycles_per_line*4), display_type);
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for(int c = 0; c < 16; c++)
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{
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_colours[c] = (uint8_t)((luminances[c] << 4) | chrominances[c]);
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}
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}
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/*!
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Impliedly runs the 6560 for a single cycle, returning the next address that it puts on the bus.
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*/
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uint16_t get_address()
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{
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// keep track of the amount of time since the speaker was updated; lazy updates are applied
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_cycles_since_speaker_update++;
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// keep an old copy of the vertical count because that test is a cycle later than the actual changes
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int previous_vertical_counter = _vertical_counter;
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// keep track of internal time relative to this scanline
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_horizontal_counter++;
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_full_frame_counter++;
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if(_horizontal_counter == _timing.cycles_per_line)
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{
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if(_horizontal_drawing_latch)
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{
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_current_character_row++;
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if(
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(_current_character_row == 16) ||
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(_current_character_row == 8 && !_registers.tall_characters)
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) {
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_current_character_row = 0;
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_current_row++;
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}
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_pixel_line_cycle = -1;
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_columns_this_line = -1;
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_column_counter = -1;
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}
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_horizontal_counter = 0;
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_horizontal_drawing_latch = false;
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_vertical_counter ++;
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if(_vertical_counter == (_registers.interlaced ? (_is_odd_frame ? 262 : 263) : _timing.lines_per_progressive_field))
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{
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_vertical_counter = 0;
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_full_frame_counter = 0;
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_is_odd_frame ^= true;
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_current_row = 0;
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_rows_this_field = -1;
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_vertical_drawing_latch = false;
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_base_video_matrix_address_counter = 0;
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_current_character_row = 0;
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}
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}
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// check for vertical starting events
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_vertical_drawing_latch |= _registers.first_row_location == (previous_vertical_counter >> 1);
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_horizontal_drawing_latch |= _vertical_drawing_latch && (_horizontal_counter == _registers.first_column_location);
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if(_pixel_line_cycle >= 0) _pixel_line_cycle++;
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switch(_pixel_line_cycle)
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{
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case -1:
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if(_horizontal_drawing_latch)
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{
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_pixel_line_cycle = 0;
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_video_matrix_address_counter = _base_video_matrix_address_counter;
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}
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break;
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case 1: _columns_this_line = _registers.number_of_columns; break;
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case 2: if(_rows_this_field < 0) _rows_this_field = _registers.number_of_rows; break;
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case 3: if(_current_row < _rows_this_field) _column_counter = 0; break;
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}
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uint16_t fetch_address = 0x1c;
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if(_column_counter >= 0 && _column_counter < _columns_this_line*2)
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{
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if(_column_counter&1)
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{
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fetch_address = _registers.character_cell_start_address + (_character_code*(_registers.tall_characters ? 16 : 8)) + _current_character_row;
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}
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else
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{
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fetch_address = (uint16_t)(_registers.video_matrix_start_address + _video_matrix_address_counter);
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_video_matrix_address_counter++;
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if(
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(_current_character_row == 15) ||
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(_current_character_row == 7 && !_registers.tall_characters)
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) {
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_base_video_matrix_address_counter = _video_matrix_address_counter;
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}
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}
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}
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return fetch_address & 0x3fff;
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}
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/*!
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An owning machine should determine the state of the data bus as a result of the access implied
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by @c get_address and supply it to set_graphics_value.
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*/
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void set_graphics_value(uint8_t value, uint8_t colour_value)
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{
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// TODO: there should be a further two-cycle delay on pixels being output; the reverse bit should
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// divide the byte it is set for 3:1 and then continue as usual.
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// determine output state; colour burst and sync timing are currently a guess
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if(_horizontal_counter > _timing.cycles_per_line-4) _this_state = State::ColourBurst;
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else if(_horizontal_counter > _timing.cycles_per_line-7) _this_state = State::Sync;
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else
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{
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_this_state = (_column_counter >= 0 && _column_counter < _columns_this_line*2) ? State::Pixels : State::Border;
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}
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// apply vertical sync
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if(
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(_vertical_counter < 3 && (_is_odd_frame || !_registers.interlaced)) ||
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(_registers.interlaced &&
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(
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(_vertical_counter == 0 && _horizontal_counter > 32) ||
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(_vertical_counter == 1) || (_vertical_counter == 2) ||
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(_vertical_counter == 3 && _horizontal_counter <= 32)
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)
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))
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_this_state = State::Sync;
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// update the CRT
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if(_this_state != _output_state)
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{
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switch(_output_state)
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{
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case State::Sync: _crt->output_sync(_cycles_in_state * 4); break;
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case State::ColourBurst: _crt->output_colour_burst(_cycles_in_state * 4, _is_odd_frame ? 128 : 0, 0); break;
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case State::Border: output_border(_cycles_in_state * 4); break;
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case State::Pixels: _crt->output_data(_cycles_in_state * 4, 1); break;
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}
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_output_state = _this_state;
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_cycles_in_state = 0;
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pixel_pointer = nullptr;
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if(_output_state == State::Pixels)
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{
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pixel_pointer = _crt->allocate_write_area(260);
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}
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}
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_cycles_in_state++;
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if(_this_state == State::Pixels)
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{
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if(_column_counter&1)
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{
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_character_value = value;
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if(pixel_pointer)
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{
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uint8_t cell_colour = _colours[_character_colour & 0x7];
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if(!(_character_colour&0x8))
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{
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uint8_t colours[2];
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if(_registers.invertedCells)
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{
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colours[0] = cell_colour;
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colours[1] = _registers.backgroundColour;
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}
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else
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{
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colours[0] = _registers.backgroundColour;
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colours[1] = cell_colour;
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}
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pixel_pointer[0] = colours[(_character_value >> 7)&1];
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pixel_pointer[1] = colours[(_character_value >> 6)&1];
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pixel_pointer[2] = colours[(_character_value >> 5)&1];
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pixel_pointer[3] = colours[(_character_value >> 4)&1];
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pixel_pointer[4] = colours[(_character_value >> 3)&1];
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pixel_pointer[5] = colours[(_character_value >> 2)&1];
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pixel_pointer[6] = colours[(_character_value >> 1)&1];
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pixel_pointer[7] = colours[(_character_value >> 0)&1];
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}
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else
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{
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uint8_t colours[4] = {_registers.backgroundColour, _registers.borderColour, cell_colour, _registers.auxiliary_colour};
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pixel_pointer[0] =
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pixel_pointer[1] = colours[(_character_value >> 6)&3];
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pixel_pointer[2] =
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pixel_pointer[3] = colours[(_character_value >> 4)&3];
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pixel_pointer[4] =
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pixel_pointer[5] = colours[(_character_value >> 2)&3];
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pixel_pointer[6] =
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pixel_pointer[7] = colours[(_character_value >> 0)&3];
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}
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pixel_pointer += 8;
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}
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}
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else
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{
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_character_code = value;
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_character_colour = colour_value;
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}
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_column_counter++;
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}
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}
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/*!
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Causes the 6560 to flush as much pending CRT and speaker communications as possible.
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*/
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inline void synchronise() { update_audio(); }
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/*!
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Writes to a 6560 register.
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*/
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void set_register(int address, uint8_t value)
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{
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address &= 0xf;
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_registers.direct_values[address] = value;
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switch(address)
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{
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case 0x0:
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_registers.interlaced = !!(value&0x80) && _timing.supports_interlacing;
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_registers.first_column_location = value & 0x7f;
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break;
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case 0x1:
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_registers.first_row_location = value;
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break;
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case 0x2:
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_registers.number_of_columns = value & 0x7f;
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_registers.video_matrix_start_address = (uint16_t)((_registers.video_matrix_start_address & 0x3c00) | ((value & 0x80) << 2));
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break;
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case 0x3:
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_registers.number_of_rows = (value >> 1)&0x3f;
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_registers.tall_characters = !!(value&0x01);
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break;
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case 0x5:
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_registers.character_cell_start_address = (uint16_t)((value & 0x0f) << 10);
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_registers.video_matrix_start_address = (uint16_t)((_registers.video_matrix_start_address & 0x0200) | ((value & 0xf0) << 6));
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break;
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case 0xa:
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case 0xb:
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case 0xc:
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case 0xd:
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update_audio();
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_speaker->set_control(address - 0xa, value);
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break;
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case 0xe:
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update_audio();
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_registers.auxiliary_colour = _colours[value >> 4];
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_speaker->set_volume(value & 0xf);
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break;
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case 0xf:
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{
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uint8_t new_border_colour = _colours[value & 0x07];
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if(_this_state == State::Border && new_border_colour != _registers.borderColour)
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{
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output_border(_cycles_in_state * 4);
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_cycles_in_state = 0;
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}
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_registers.invertedCells = !((value >> 3)&1);
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_registers.borderColour = new_border_colour;
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_registers.backgroundColour = _colours[value >> 4];
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}
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break;
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// TODO: the lightpen, etc
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default:
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break;
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}
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}
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/*
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Reads from a 6560 register.
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*/
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uint8_t get_register(int address)
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{
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address &= 0xf;
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int current_line = (_full_frame_counter + _timing.line_counter_increment_offset) / _timing.cycles_per_line;
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switch(address)
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{
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default: return _registers.direct_values[address];
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case 0x03: return (uint8_t)(current_line << 7) | (_registers.direct_values[3] & 0x7f);
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case 0x04: return (current_line >> 1) & 0xff;
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}
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}
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private:
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std::shared_ptr<Outputs::CRT::CRT> _crt;
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// audio state
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class Speaker: public ::Outputs::Filter<Speaker> {
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public:
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Speaker();
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void set_volume(uint8_t volume);
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void set_control(int channel, uint8_t value);
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void get_samples(unsigned int number_of_samples, int16_t *target);
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void skip_samples(unsigned int number_of_samples);
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private:
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unsigned int _counters[4];
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unsigned int _shift_registers[4];
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uint8_t _control_registers[4];
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uint8_t _volume;
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};
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std::shared_ptr<Speaker> _speaker;
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unsigned int _cycles_since_speaker_update;
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void update_audio()
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{
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_speaker->run_for_cycles(_cycles_since_speaker_update >> 2);
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_cycles_since_speaker_update &= 3;
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}
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// register state
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struct {
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bool interlaced, tall_characters;
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uint8_t first_column_location, first_row_location;
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uint8_t number_of_columns, number_of_rows;
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uint16_t character_cell_start_address, video_matrix_start_address;
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uint8_t backgroundColour, borderColour, auxiliary_colour;
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bool invertedCells;
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uint8_t direct_values[16];
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} _registers;
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// output state
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enum State {
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Sync, ColourBurst, Border, Pixels
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} _this_state, _output_state;
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unsigned int _cycles_in_state;
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// counters that cover an entire field
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int _horizontal_counter, _vertical_counter, _full_frame_counter;
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// latches dictating start and length of drawing
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bool _vertical_drawing_latch, _horizontal_drawing_latch;
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int _rows_this_field, _columns_this_line;
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// current drawing position counter
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int _pixel_line_cycle, _column_counter;
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int _current_row;
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uint16_t _current_character_row;
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uint16_t _video_matrix_address_counter, _base_video_matrix_address_counter;
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// data latched from the bus
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uint8_t _character_code, _character_colour, _character_value;
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bool _is_odd_frame;
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// lookup table from 6560 colour index to appropriate PAL/NTSC value
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uint8_t _colours[16];
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uint8_t *pixel_pointer;
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void output_border(unsigned int number_of_cycles)
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{
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uint8_t *colour_pointer = _crt->allocate_write_area(1);
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if(colour_pointer) *colour_pointer = _registers.borderColour;
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_crt->output_level(number_of_cycles);
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}
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struct {
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int cycles_per_line;
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int line_counter_increment_offset;
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int lines_per_progressive_field;
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bool supports_interlacing;
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} _timing;
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};
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}
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#endif /* _560_hpp */
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